Most strokes are caused by blockage in an artery in the brain, caused by a blood clot, resulting in tissue death. Very early use of clotbusting (thrombolytic) drugs can restore the blood supply and limit the damage, resulting in an increased proportion of people making a recovery to independence after stroke. However, these drugs only succeed in restoring blood flow in a minority of people with clots in the larger arteries (10-25% depending on the size of the blood vessel) and these people also have the most severe strokes and highest risk of death or dependence as a result of the stroke. Current best treatment is therefore least effective in the group with the most severe strokes.
An alternative approach is to use a clot removal device that can be fed through the blood vessels to either remove or break up the blood clot (mechanical thrombectomy devices). Some small studies have shown them to be effective at opening large arteries, in some cases much more effective than drug treatments. However, using these devices is a highly skilled procedure and it takes some time both to set up the necessary facilities (including anaesethetic, nurses and medical support) and to reach the blockage. The extra time that is required to use these devices may mean that brain tissue is already irreversibly damaged. If so, then an individual patient cannot benefit and indeed may be harmed by opening the artery. There are no completed clinical trials comparing the outcome in people treated with standard stroke treatment and those treated with devices.
PISTE is a randomised, controlled trial to test whether additional mechanical thrombectomy device treatment improves functional outcome in patients with large artery occlusion who are given IV thrombolytic drug treatment as standard care.
Stroke is the leading cause of adult disability in the UK and the fourth leading cause of death. The costs of stroke are estimated to be between £3.7 billion and £8 billion. The KEY current clinical question in acute stroke management is whether a treatment policy of intra-arterial thrombectomy (IAT) added to IV thrombolysis (IVT) improve clinical outcomes over IVT alone. If the answer is yes and it applies to most patients with large vessel occlusive stroke, then the implications for acute stroke care and NHS services are enormous.